This invention relates to a method of melting a metal, more particularly to a method of melting a metal by heating it directly with the flame from a fuel burner using a gas containing at least 60% of oxygen as a combustion assisting gas.
While an electric furnace is mainly used for melting metals, particularly iron scraps, recently an oxygen-assisted fuel burner in which a liquid fuel such as heavy oil is burned with the aid of oxygen is additionally used. Such a burner is used in order to accelerate the melting speed in the electric furnace as well as to obviate so-called cold spots in the metals. Meanwhile, the oxygen injection method is also employed as a technique of enhancing productivity. In this method, oxygen is injected into the melt in the furnace to effect an oxidation reaction whereby to melt the scrap by the heat of reaction.
However, the first method of melting a metal using an electric furnace described above involves a disadvantage that cold spots are inevitably left in the metal and that it must resort to the electric power as the source of energy, although it has an advantage that it can readily yield a high temperature and allows easy temperature adjustment. Meanwhile, in the second method in which an oxygen-assisted fuel burner is used in addition to the electric furnace, 60 to 80% of the total energy used is from electric power, and besides it is well known that the energy efficiency of the electric power is only about 20 to 25%, when generating efficiency, melting efficiency, etc. are all taken into consideration. In addition, referring to the generation of CO.sub.2 gas which is notorious as a causative of global environmental disruption, it is reported that about 150 m.sup.3 of CO.sub.2 is generated for melting 1 ton of metal scraps utilizing the electric power generated by use of heavy oils, so that a countermeasure therefor must be taken.
In the oxygen injection method, the above problems can be cleared since no electric power is employed. However, in this method, oxygen, a micropowdery coal and coke are injected to the melt to carry out an oxidation reaction and effect melting of the metal, so that a portion of the melt must constantly be allowed to remain in the melting furnace. This may cause no problem when the melting operation is carried out continuously, but inevitably yields poor productivity in the case of a batchwise melting operation or of intermittent melting operation, since the melt cannot entirely be removed from the melting furnace.